Optical imaging system

ABSTRACT

An optical imaging system including a document supporting surface, a short conjugate imaging device and a cylindrically shaped light responsive member. The document to be reproduced is fixedly supported adjacent the light responsive member with the imaging device therebetween. The imaging device is moved in the direction opposite the direction of rotation of the light responsive member in an arcuate path concentric with the light responsive member and document supporting surface to thereby create a usable pattern on the surface of the light responsive member in conformity with the document being reproduced.

i United States Patent Lewis et al.

[ 1 Mar. 21, 1972 [54] OPTICAL IMAGING SYSTEM [72] Inventors: William G.Lewis, Rochester; Robert W. Moorhusen, Penfield; Richard H. Nagel,

Fairfield, all of NY.

[73] Assignee: XeroxCorporation, Rochester, NY.

[22] Filed: Mar. 28, 1969 [2l] Appl.No.: 811,561

[52] US. Cl ..355/8, 355/47 [51] Int. Cl. ..G03b 27/50 [58] FieldotSearch ..355/8,52, 47, 48

[56] References Cited UNITED STATES PATENTS 3,221,622 12/1965 Aser et al..355/8 FOREIGN PATENTS OR APPLICATIONS l,l25,887 9/1968 Great Britain..355/5l 6,515,110 11/1965 Netherlands ..355/51 Primary Examiner-John M,Horan Assistant ExaminerMichael Harris Att0meyPaul M. Enlow, Norman E.Schrader, James J. Ralabate, Ronald Zibelli, Michael J. Colitz, Jr. andMichael H. Shanahan [5 7] ABSTRACT An optical imaging system including adocument supporting surface, a short conjugate imaging device and acylindrically shaped light responsive member. The document to bereproduced is fixedly supported adjacent the light responsive memberwith the imaging device therebetween. The imaging device is moved in thedirection opposite the direction of rotation of the light responsivemember in an arcuate path concentric with the light responsive memberand document supporting surface to thereby create a usable pattern onthe surface of the light responsive member in conformity with thedocument being reproduced.

1 Claims, 2 Drawing Figures Patented MarIl 21, 1972 2 Sheets-Sheet lINVENTORS' ROBERT W. MOORHUSEN WILLIAM G. LEWIS RICHARD H. NAGELATTORNEY Pa tented March 21, 1972 2 Sheets-Sheet 2 OPTICAL IMAGINGSYSTEM This invention relates to a short conjugate length imaging systemand in particular to an imaging system wherein an immo'vably supporteddocument is imaged onto a moving light responsive surface by a shortconjugate length imaging device moving therebetween.

In'the process of xerography, as described in US. Pat. No. 2,297,691 toChester F. Carlson, a xerographic surface com prising a layer ofphotoconductive insulating material affixed to. a conductive backing isused to support electrostatic images. In the usual method of carryingout the process, the xerographic surface is electrostatically chargeduniformly over its surface and then exposed to a light patternof theimage being reproduced to thereby discharge the charge in the areaswhere light strikes the layer. The undischarged areas of the layer thusform an electrostatic charge pattern in conformity with theconfiguration of the original light pattern.

The latent electrostatic image can be then developedby contacting itwith a finely divided electrostatically attractable material such aspowder. The powder is held in image areas by the electrostatic chargesonthe layer. Where the charge field is greatest, the greatest amount ofmaterial is deposited; where the charge field'is least, little or nomaterial is deposited. Thus a powder image is produced in conformitywith the light image v of copy being reproduced. The powder may then besubsequently transferred to a sheet of paper or other surface andaffixed thereto to forma permanent print. p 7

Most commercial xerographic reproducing machines in use today employimaging systems requiring a large conjugate length between 'the'original document'and light responsive surface. In general, thisdistancemust be about equal to twice the length of the diagonal of the documentor portion thereof being imaged. With the trend toward more compactreproducing machines, it has-been found desirable to employ imagingsystems which could permit the reduction of the conjugate lengthandconsequently the size of the imaging zone.

Imaging systems capable of projecting light images of an originaldocument onto a light responsive member held a short distance away aredescribed in pending applications Ser. Nos. 683,988 filed Nov. 17, I967in the name of Osmar A. Ullrich, Jr.',' et al. 683,837 filed Nov. 17,1967 in the name of Robert W. Gun dlach and 683,987 filed Nov. 17, 1967in the name of Robert W. Gundlachet al. According to those disclosures,it is necessary to support the object being reproduced and the lightresponsive surface immovable with respect to each other during imaging.Imaging occurs in a flowing manner as the object and image surfaces areheld fixed and the imaging device moves relative .thereto. The imagedsurface may then be developed and transferred to the final backingsheet.

Another short conjugate length optical imaging system is disclosed inCanadian Pat. No. 771,916 issued Nov. 21, 1967 in the name of Kaufer etal. In that disclosure, it is necessary to move both the lightresponsive surface and document being reproduced in opposite directionswith respect to each other to effect correct imaging. The imaged sheetmay then be developed to constitute the final copy.

Such prior art imaging systems are not universally suited for use incontinuous and automatic xerographic reproducingmachines. For example,expanded utility of the reproducing machine may be attained if theelements of the imaging station may be made to function in a continuousmode as the other xerographic processing stations.

This continuous mode cannot necessarily be attained if the lightreceiving surface must be stopped during the imaging step. Furthermore,the utility of a reproducing machine may be expanded if the original tobe copied is held stationary during its imaging. When an imaging systempermits the scanning of a fixed original, it then becomes easier tocreate copies of three-dimensional objects or the'like. In such afixed-original system, document handling is also minimized since thedocuments need never be grasped or forwarded by document handlingmechanisms.

It is therefore an object of the instant invention to optically projectan image of an object to be reproduced .onto a light responsive memberwith a short distance therebetween.

It is a further object of the instant invention to flowingly image lightrays of a fixedly supported object onto a moving light responsive memberby projection along a short conjugate length. I

It is a further object of the instant invention to dissipate anelectrostatic charge on a rotating cylindrically shaped light responsivemember in accordancev with a light pattern projected from a documentwhich is immovably supported.

' It is a furtherobject of the instant invention to create anelectrostatic charge pattern on a light responsive surface of a rotatingcylinder through a short conjugate length imaging system moving betweenthe cylinder, and a fixed document lengthimaging device and acylindricallyshaped light responsive member. The document to bereproduced is fixedly su-pported-adjacent the light responsive surfacewith the short conjugate length imaging device therebetween. The imagingdevice is moved in the direction opposite the direction of rotation ofthe light responsive surface in an arcuate path concentric with thelight responsive member and document supporting surface to therebycreate a usable pattern on the surface of the light responsive member inconformity with the document being reproduced. v

Further objects together with additional features and advantages thereofwill become apparent from the following description of one embodiment ofthe invention when read in conjunction with the accompanying'drawingswherein: FIG. 1 is a schematic representation of a continuous andautomatic xerographic reproducing machine employing the imaging systemof the instant invention and FIG. 2 is a perspective view of the imagingsystem shown in FIG. 1. t 1

Referring now to the drawings, there is shown an-embodiment of thesubject invention in a suitable environment such as an automaticxerographic reproducing machine. The auto- I matic xerographicreproducing machine includes light responsive member 10 in the form of axerographic plate or surface formed in the cylindrical shape of a drum.The plate has a photoconductive layer or light receiving surface on aconductive backing supported by drive shaft 12 journaled in the machineframe to rotate under the influence of a suitable power source, notshown, in the direction indicated by the arrow. The rotation will causethe plate surface to sequentially pass a series of xerographicprocessing station's. While the light responsive surface is shown as axerographic surface it could be any light responsive surface, as forexample, a photographic film.

For the purposes of the present disclosure, the several xerographicprocessing stations in the path of movement of the plate surface may bedescribed functionally as follows:

A charging station ,A, at which a uniform electrostatic charge isdeposited on the photoconductive plate;

An exposure station B, at which light or radiation pattern of copy to bereproduced is projected onto the plate surface to dissipate the chargein the exposed areas thereof to thereby form a latent electrostaticimage of the copy to be reproduced;

A developing station C at which xerographic developing material,including toner particles having an electrostatic charge opposite thatof the latent electrostatic image, is cascaded over the plate surfacewhereby the toner particles adhere to the latent electrostatic image toform a toner image in the configuration of the copy being reproduced;

A transfer station D at which the toner image is electrostaticallytransferred from the plate surface to a transfer material or a supportsurface; and

A drum cleaning and discharge station E at which the plate surface isbrushed to remove residual toner particles remaining thereon after imagetransfer.

It is felt that the preceding description of the xerographic process issufficient for an understanding of the instant invention.

In order to operate the imaging system of the instant invention it isfirst necessary to place the document or object to be reproduced on thetransparent document supporting surface 14 in the object plane. Thedocument supporting surface is in a curved orientation concentric withthe portion of the cylindrical xerographic member passed through theimage plane in the imaging zone 16. The xerographic member need not bein the shape of a right circular cylinder. It could readily be anendless belt with a curved portion thereof passing through the imagingzone. Positioned between the document supporting surface 14 and thelight responsive member 10 is the optical imaging device 18.

The imaging device is constructed in accordance with that disclosed inthe aforementioned Gundlach et al. application. This device includes aplurality of transparent light refracting lens strips 20, 22 and 24having lens portions 26 formed thereon. Lens strip is positioned twofocal lengths away from the object to be reproduced as well as theintermediate field lens 22. The lens portions 26 of this lens strip 20are adapted to project light images from the document and toindividually invert and revert the scanned segments of the image.

The lens strip 24, positioned two focal lengths away from the lightresponsive surface and intermediate field lens 22 will, in like turninvert and revert the images formed adjacent the field lens 22 toultimately project ,upright wrong reading images of the scanned portionsof the document onto the light responsive surface 10. This will therebydischarge the original charge on the drum into a latent electrostaticimage corresponding to the document being reproduced. An aperture stop28 and field stop 30 limit the intensity and amount of light projectedfrom the document to the light receiving surface for ensuring an evenimaging of the document across the drum. The aforementioned focallengths and other parameters of the imaging elements are by way ofexample only since other lens stip configurations, including thosecreating reduced intermediate images, may be readily employed.

The various optical imaging elements including the lens strips and stopsare secured in position with respect to each other by side support platemembers 32 and light shielding plate members 34 which, like the lensstrips, extend the length of the drum and document supporting surfacethereby ensuring that the entire length of the document will beprojected and imaged onto the xerographic surface. End support plates 36support these side frames and imaging elements with respect to eachother and define a light-shielded tunnel from an area adjacent thedocument supporting surface and xerographic drum. Tie rods 38 lendsupport to the assembly.

The end support plates 36 are mounted on shaft 12 for rotationalmovement in an arc concentric with the document supporting surface anddrum shaped light responsive member. In this manner, the distancebetween the first lens strip 20 and that portion of the documentsupported on the document supporting surface being imaged can bemaintained substantially constant during the oscillation of the imagingdevice. This ar-' rangement also ensures that the distance between thelens strip 24 and the xerographic surface being imaged is, in likefashion, held at a substantially fixed distance during operation of thedevice. The ends of the side support plates 36, remote from the drum,also support lamps 40 which illuminate the object during imaging.

One of the end support plates 36 has a sprocket 42 secured theretocooperable with chain 44 which is in turn coupled to reversible motorMOT-l to impart cyclical oscillating scanning motion to the imagingdevice.

The xerographic reproducing machine is started by activating the variousprocessing stations including the imaging station. The drum shaped lightresponsive member 10 is then rotated on the power imparting shaft 12 byits suitable power source to rotate a charged portion of the drum in thedirection of thearrow to sequentially bring portions of the drum surfacebeneath the charging station to provide the uniform charge on the drum.When the leading edge of the charged portion of the surface approachesthe exit end 46 of the imaging zone 16, power source MOT-l will beenergized to start the imaging device to move in a direction oppositefrom the direction of rotation of the drum to thereby sequentially imagethe original document onto the drum in a flowingly fashion. After theimaging device 18 has traversed to the drum input end 48 of the imagingzone its motion will be reversed by the action of its motor to itsstart-of-scan position to begin a second imaging of a subsequent sectionof the xerographic surface 10. The return, or fly back, speed of theimaging device may be equal to the speed of the light responsive memberto thereby facilitate the next start-of-scan on a segment of the lightresponsive member contiguous with that previously imaged. The machinecould readily be programmed to stop after this or a predetermined numberof cycles of the imaging device and consequently stop the creation ofelectrostatic images on the drum after a predetermined number of imagingcycles.

The imaged portion of the drum is then developed, transferred to abacking material such as a web 50 or a cut sheet synchronouslycontacting the image for fusing to create the final copy. The drum isthen passed through the cleaning station prior to subsequent chargingand imaging in a continuous and automatic cycle of operation.

The general speed of scan relationship for the instant embodiment may beexpressed as a,B=(r r )/r, wherein a is the rotational speed of thelight responsive member, [3 is the rotational speed of the imagingdevice and r, and r are the distances from the center of curvature ofthe light responsive surface to the light responsive surface and to theobject plane, respectively.

In one specific example for operating the imaging system of the instantinvention, a 6-inch diameter drum was employed with the documentsupporting surface located to place the image in an arc 10 inches fromthe center or rotation of the xerographic drum. A lens strip was thenpositioned therebetween with the lens strips equally positioned withrespect to each other as well as the document to be reproduced and thesurface of the xerographic drum.

The drum was then rotated at 6.28 inches per second at its surface in aclockwise direction as shown in HO. 1 while the imaging device wasrotated at a linear speed of 8.97 inches per second at its extreme or10-inch radius. The lens strip imaging device effectively traveled 2.69inches per second at the 3- inch drum radius during the same 1 second inwhich the drum rotated 6.28 inches. In all, the drum had effectivelytraveled 8.97 inches with respect to the document during the same timethat the lens strip traversed the entire length of the document.

While the instant invention has been described as carried out in aspecific embodiment hereof, it is not intended to be limited thereby butit is intended to be protected broadly within the scope of the appendedclaims.

What is claimed is:

1. For use in the imaging station of a reproducing machine wherein afixedly supported document is sequentially scanned by an optical systemto produce a useable image pattern on a light responsive surface movingthrough the imaging station the combination including,

a document supporting surface having an arcuate cross-sectionalconfiguration adapted to have a document to be reproduced fixedlypositioned thereon,

a light responsive member positioned adjacent said document supportingsurface to define an imaging zone therebetween, said light responsivemember having a curved cross-sectional configuration in the imaging zoneconcentric with the document supporting surface,

an imaging device positioned in the imaging zone, said imaging deviceincluding a plurality of transparent strips having lens surfaces formedthereon, said lens strip closest to said document supporting surfaceadapted to invert and revert light rays moving toward said lightresponsive member, said lens strip closest said light responsive surfacebeing adapted to invert and revert posite the direction of movement ofsaid light responsive member in a path of movement concentric with saiddocument supporting surface to thereby create a flowing representationof the imaged document on said light responsive surface, the speed ofsaid imaging device and said light responsive member being correlated tomaintain a 1:1 reproduction of the original document.

1. For use in the imaging station of a reproducing machine wherein afixedly supported document is sequentially scanned by an optical systemto produce a useable image pattern on a light responsive surface movingthrough the imaging station the combination including, a documentsupporting surface having an arcuate cross-sectional configurationadapted to have a document to be reproduced fixedly positioned thereon,a light responsive member positioned adjacent said document supportingsurface to define an imaging zone therebetween, said light responsivemember having a curved cross-sectional configuration in the imaging zoneconcentric with the document supporting surface, an imaging devicepositioned in the imaging zone, said imaging device including aplurality of transparent strips having lens surfaces formed thereon,said lens strip closest to said document supporting surface adapted toinvert and revert light rays moving toward said light responsive member,said lens strip closest said light responsive surface being adapted toinvert and revert light rays past through said first lens strip andthereby project an upright wrong reading image toward said lightresponsive member, means to move said light responsive member in a firstdirection through said imaging zone in a path concentric with thedocument supporting surface while said lens strips are projecting lightimages theretowards, and means to move said imaging device in adirection opposite the direction of movement of said light responsivemember in a path of movement concentric with said document supportingsurface to thereby create a flowing representation of the imageddocument on said light responsive surface, the speed of said imagingdevice and said light responsive member being correlated to maintain a1:1 reproduction of the original document.